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Red Apple- Downy Mildew & Fusarium

 Is your red apple suddenly looking sick, or dying? Does the red apple have dead patches, spotting, discoloration.

Historically, Red Apple has been widely grown and thrived in our region due to its hardiness.
Starting in late 2015 a foliar pathogen known as Downy Mildew disease was first discovered in our region. Since then this “water mold disease” has spread throughout Southern California.

It is now being found that as the leaf decomposes, the “down” spores disappear and are replaced by secondary fungi (such as Fusarium sp.) that thrive on damaged or dead tissue. In addition the same symptoms are now being reported on the Delosperma and Lampranthus varieties of Iceplant.

Red apple slope with Downey Mildew, before any applications

Red apple slope with Downy Mildew, before any applications

Downy Mildew‐ Is closer related to algae (water mold) than a fungi. Spores thrive under wet and cool conditions. Symptoms include leaf discoloration and spotting, along with die-back of the iceplant from the youngest tips back down the stem.

Fusarium‐ Will cause die-back, and eventually kill the entire stem and plant. The extent of damage and plant recovery and re‐growth are still being studied.

Fusarium sp. on Red Apple

Management:

  • Good cultural practices and sanitation can minimize downy mildew of ice plants.
  • Avoid overhead irrigation during cool weather. Consider watering in the morning hours so that plants dry during the day.
  • If severely infected, remove and destroy plants with advanced symptoms of infection.
Red apple slope after two fungicide applications

Red apple slope after two fungicide applications

Treatment:

A comprehensive management plan is required to help save large plantings. Downy mildew evolves very quickly to form new races and can rapidly develop fungicide resistance. A proper fungicide program with multiple alternating fungicides is recommended to be applied by a professional applicator.

 

For more information please visit

http://blogs.cdfa.ca.gov/Section3162/?tag=peronospora-mesembryanthemi

 

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=20558